$ { \left[\begin{array}{rr}{-1} & {0} \\ {0} & {-2}\end{array}\right]+\left[\begin{array}{rr}{-1} & {4} \\ {2} & {3}\end{array}\right] = {?} } $
To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{-1}+{-1} & {0}+{4} \\ {0}+{2} & {-2}+{3}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-2} & {4} \\ {2} & {1}\end{array}\right]}$